Method for casting pipes



Feb. 14, 1933.

S. B. CLARK METHOD FOR CASTING PIPES Filed May 9, 1951 Patented Feb. 14,1933 UNITED ASTATES STUART B. CLARK, F RIVERTON, NEW .TER FOUNDRYCOMPANY, OF BURLINGTON,

JERSEY' SEY, ASSIGNOR T0 UNITED STATES PIPE &

NEW JERSEY, A CORPORATION OF NEW METHOD FOR CASTING PIPES Applicationled Hay 9, 1931. Serial No. 536,159. I

My invention has relation to the well known method of casting pipes inwhich their power driven rotatable mold is associated with a relativelyretractable runner for delivering molten metal to the mold, which at thebeginning of the casting operation is fully inserted in the mold so asto deliver metal to its remote end and which is retracted during thepouring operation so as to deliver the metal pro ressively throughoutthe length of the mol A typical machine adapted for the practice of thismethod of castin pipes is described in Patent No. 1,746,3 4, granted toJ. H. Uhrig, February l1, 1930. In the operation of such a machine it iscustomary to have the moldslightly tilted from the horizontal tofacilitate the pouring operation and in consequence 'the iow of themetal delivered to the rotating mold is inuenced not only by thecentrifugal force applied to it by the rotating mold but also to someextent by gravity tending to cause the metal to flow in the direction ofthe lower end of the mold, so that there is a certain longitudinalshifting of the molten metal in the mold during the casting operationwhich is unobjectionable during the casting of the main body of the pipebut which during the casting of the final end of the pipe sometimesresults in the thinning down of this end of the pipe to an objectionableextent. y

While it is perhaps obvious that the tendency of the molten metal tofiow longitudinally in the mold can be Vcounteracted to a large extentby increasing the speed of rotation of the mold, it has been found thatmaterial increase in the rotative speed of the mold over that found tobe efficient in practice brings about a tendency to slip between themold and the casting, which is apt to result in a defective casting.

The object of my invention is to provide an improved method whereby' theliability of the process as heretofore carried on to produce pipes withthin or defective final ends can be greatly diminished and this I havefound can be accomplished by increasing the rotative speed of the moldduring the pouring of the final end of the .pipe only, so

as to materially diminish the tendency to longitudinal downward How ofthe metal during this stage of the casting operation and thereby insurethat to a much greater extent than heretofore the metal poured into thisfinal end of the mold will have a greatly diminished tendency towardsgravital flow in the mold and I have discovered that this increasedrotative speed of the mold during the final stage of the pouring of thepipe can be effected without material tendency to cause a slip betweenthe mold and the casting.

y invention therefore consists, broadly speaking, in the improvement inthe described method of centrifugal casting of pipe which consists inincreasing the rotative speed of the mold during the final stages of thepipe casting operation so as to counteract to a large degree thetendency of the metal to flow gravitally during this stage of thecasting operation.

In practice I have found it desirable and practicable to increase 'thespeed of rotation of the mold in many instances during the casting ofthe final end of the pipe to an extent of from to 50% approximately ofthe normal speed of rotation during the greater part of the castingoperation. The extent to which the mold rotation is increased and thelocation of such point of increase with reference to relative positionof mold and runner depends largely on the fiuidity of the iron and othervariable characteristics of the iron and casting conditions. Foraconcrete example, in the casting of a six inch pipe I increase the speedof rotation during this stage of the casting operation from the normalspeed of 500 revolutions er minute to 600 revolutions per minute, withthe result that the production of defective pipes is ma' teriallyreduced.

To provide for the most eicient application of my improved method I havedevised automatically acting means for-. increasing the speed ofrotation of the mold during the final stage of the pipe castingoperation and for this purpose I provide a device arranged to operatein'timed relation with the retractive movements of the mold and runnerand so connected with the rotating drivto which my invention pertainsand' of au- ,I gear connected with is of such length tomatic means foractuating the switch at a given point in the travel of the mold, and

Figure 2 is a diagrammatic showing of an electric system for controllingthe speed of the motor.

In the drawing, A indicates the base of the machine which supportstracks or runners indicated at B, upon which a carriage C is movable,the tracks being inclined, as indicated, to anangle of about 2 to ahorizontal plane. The carriage C supports a water box D, through whichextends the centrifugal pipe mold E and the end E1 of the mold is aVariable speed electric motor, indicated at F, so as to rotate the mold.G indicates the runner through which molten metal is poured into themold, this runner being supported on the base of the machine hy a frameO, which also supports the tilting iron ladle P. This runner that itsdelivery end when the carriage is moved to the extreme upper positionextends nearly to the remote end of the mold. H is a switch operatingfinger, capable of longitudinal adjustment, secured to the mold carriageand I is an electric switch, mounted on the base A, and connectingelectrically with the control panel ofv motor F. As shown in Fig. 2, thefield of the motor has in serieswith it a variable resistance J. Theswitch I is normall closed, which energizes a solenoid switch to hold itin closed position, and the field circuit is from the line through lineL, switch K, line M, a portion of resistance J the field and back to theother side of he line. The amount of resistance cut in here determinesthe speed of the motor, it being understood that the greater theresistance in the field circuit the greater the speed of the motor.

In operation, the mold, being moved to the position in which the runnerextends through its length, is actuated at normal speed by t e variablespeed electric motor F and metal is delivered to the runner G by ladle Pand passes through it to the remote end of the mold. The carriagesupporting the mold is then retracted at regulated speed so that thepouring of the metal progresses throughout the length of the mold. Whenthe carriage has reached the position in which the operating finger Hengages the actuating arm of switch I, the cir'icuit controlling switchK is broken. Thereafter the 'eld circuit is compelled to take a pathfrom the line through a variable connection N to the resistance J. Thiscuts in an adjustable amount of extra resistance and the motor speeds upas desired to rotate the mold more ra idly.

The speed of the mold can of course increased by hand manipulation offield rheostat controls.

After the rotation speed of mold has been increased, such increasedspeed should be maintained until the pouring is complete.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

In the method of casting pipe in which molten metal is delivered to arapidly rotating mold maintained at a fixed slight angle of inclinationto a horizontal plane through a relatively retractable runner whichdelivers molten metal progressively toward and to the upper end of theinclined mold, the improvement which consists in increasing the rotatives ed of the mold during the casting of the al end of the pipe so as tocounteract to a large extent the tendency to a gravital flow of themetal in the mold during this stage of the casting operation.

STUART B. CLARK.

